1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a magneto-resistive (MR) sensor, and more particularly, to a MR sensor which detects a magnetic field using a change in electric resistance between two magnetic bodies that is caused by the change in an external magnetic field.
2. Description of the Related Art
Hard disk drives (HDD) are widely used as information storage devices and use magnetic material as an information recording medium. In a HDD, information is recorded by applying strong magnetic field to a local region, called a bit, of recording medium, thereby switching the magnetization direction of the region. Stored information is detected by using the magneto-resistive (MR) sensor which detects the direction and strength of the magnetic field coming out from the bit recorded on the medium. Since bit size gets smaller and smaller as recording density is increased, the magnetic signal from the recording medium also gets smaller. In order to realize high recording density, one of the critical issues is how to effectively detect the small magnetic field emanating from the small bits recorded on the medium. To enhance the detection capability of the MR sensor, various types of sensors adopting different mechanisms such as anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunneling magnetoresistance (TMR) have been developed. The initial AMR type sensor has a 1˜2% magnetoresistance ratio compared to the present GMR type sensor which has approximately a 10% magnetoresistance ratio, and currently, the TMR type sensor with approximately a 40% magnetoresistance ratio is being implemented for a read sensor for commercial magnetic heads for a HDD.
However, in order to accurately reproduce information from a magnetic recording medium having a recording density of several Tera bits per square inch (Th/in2), a new magnetic sensor with a much higher magnetoresistance ratio than as described above may be required.